By day, I'm a post audio engineer - I work in TV and Film. I mostly mix these days, but sometimes I do a bit of sound design.
Bowed gong and bowed cymbal are two of my all - time favorite SFX, especially when used in layers.
They can do many things, from scary to sunrise. - and they take effects nicely too, like flanging and verb. I have a private collection of samples, made them myself. Hint - thin and broken cymbals with lots of rosin on the bow = especially interesting sounds. Try it! You can bow glasses of water too.
Makes me wonder sometimes why Bonham didn't jump up and grab that bow from Paige when he was doing the bowed Les Paul thing...he could have done some cool(er) things with it!
Neal